Method of treating glowers for direct-current electric lamps.



No. 718,455. PATENTED JAN. 13, 1903.

M. W. HANKS. METHOD OF TREATING GLOWERS FOR DIRECT CURRENT ELECTRICLAMPS.

APPLICATION FILED MAR. 23, 1901. K0 MODEL.

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UNITED STATES l ATENT OFFICE.

MARSHALL WV. HANKS, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR TO GEORGEWVESTINGHOUSE, OF PITTSBURG, PENNSYLVANIA.

METHOD OF TREATING GLOWERS FOR DIRECT-CURRENT ELECTRIC LAMPS.

SPECIFICATION forming part of Letters Patent No. 718,455, dated January13, 1903.

Application filed March 23, 1901- Serial No. 52,651. (No specimens.)

T0 ctZZ whom it may concern:

Be it known that I, MARSHALL W. HANKs, a citizen of the United States,residing at Pittsburg, in the county of Allegheny and State ofPennsylvania, have invented new and useful Improvements in Methods ofTreating Glowers for Direct- Current Electric Lamps, of which thefollowing is a specification.

My invention or discovery relates to electric lamps of the type in whichthe lightemitting members, usually called glowers, are non-conductorswhen cold and become conductors when raised to a relatively hightemperature by means of independently-generated heat, and particularlyto methods of treating such lightemitting members or glowers prior totheir use in lamps.

The object of my invention or discovery is to so treat glowers for usein direct-current circuits that they may have long life and asubstantially constant candle-power without material change in potentialduring their terms of service.

If a new glower constructed and prepared for use in accordance with thepractice heretofore existing is put into service in a directcurrentcircuit, the potential difference between its terminals and also itscandle-power are usually found to be variable. When such a glower firstbecomes conductive, it ap pears to have a substantially uniform degreeof light emission throughout its entire length, but gradually theportion next the negative terminal decreases in brilliancy until itbecomes comparatively non-luminous, and as the length of serviceincreases the dark or relatively non-luminous portion increases inlength. While this change is in progress the potential differencebetween the glower-terminals, and consequently the current taken by theglower, willgenerally vary to a greater or less degree. The consequenceis that either the life of the glower is shortened or the efficiency ismaterially less than would be the case if the glower were uniformlyluminous and a constant potential difference were maintained between itsterminals.

I have discovered that if a glower intended for use in connection withdirect-current circuits is first heated to conducting temperature andthen'subjected to either a normal or an overload alternating current fora comparatively short time it may then be transferred to adirect-current lamp and there used satisfactorily with a minimumvariation of potential difference and candle-power.

In general the density of the alternating current employed in treating aglower and the extent of time to which it is subjected to such currentdepends upon the character of the glower and its terminals. I regard agreater or less overload-current as generally preferable to a normalcurrent, and such overload may vary with different glowers and terminalsup to forty or fifty per cent. above the normal, and the time fortreatment may vary from a very few minutes up to an hour or more. Itherefore do not desire to limit the method to the use of currents ofany specific density or to treatment for any specific length of time.The current and time are both easily ascertained by any one skilled inthe art, and when determined for one of a lot of glowers of the samekind by a suitable test the remainder of glowers of that kind may betreated in the same way.

While it is inexpedient and practically impossibleto formulate aninflexible rule governing the length of time during which the glowershall be treated and the amount of current to which it shall besubjected, for the reason that different glowers require treatments fordifferent lengths of time and with currents of diderent densities, thefollowing may be given as an example: Assuming that each of the glower-sof a certain lot will rise ten volts in one hundred hours at a normaldensity of direct current, one of these glowers may be treated byalternating current at ten per cent. overload for a period of fifteenminutes, after which it may rise only five volts in one hundred hourswhen subjected to direct current of normal density. This glower may beagain treated as before, and it is then found that its voltage remainssubstantially constant when subjected to a direct current of normaldensity for one hundred hours. The current density and the timenecessary for treating each of the remaining glowers of this lot is thusdetermined. It follows from what has been already stated that theconditions to be followed in treating any one lot of glowers must bedetermined by testing a specimen from that lot.

In the accompanying drawings I have illustrated means for practicing myinvention, Figure 1 being a diagrammatic representation of analternating-current circuit and means for connecting a glower theretofor treatment, and Fig. 2 a diagrammatic representation of a lampoperated by direct currents.

In Fig. 1 the mains 1 and 2 are indicated as supplied with energy fromthe secondary of a transformer 3. From the main 2 a conductor 4 leads toa suitable binding device 5, and from the main 1 a conductor 6 leads toa similar binding device 7. The glower 8 to be treated has its terminalsconnected to the binding devices 5 and 7.

The glower may be heated to conducting temperature by a flame or bymeans of an electric heater, as may be most convenient.

I have shown an electric heater 9, having its terminals respectivelyconnected to the conductors 4 and 6, though the heater may be suppliedfrom a separate circuit or may be so connected to the mains 1 and 2 asto be automatically cut out when the glower becomes conductive.

In Fig. 2 the mains l0 and 11 are supplied with energy from adirect-current generator 12 and the glower 13. Ballast resistance 14 andheater 15 are connected in circuit in the manner usual to lamps of thisclass, a cut-out device 16 being employed for the purpose ofautomatically interrupting the heater-circuit when the glower becomesconductive.

I claim as my invention- 1. Themethod of treatingglowers to be used indirect-current lamps which consists in first heating them to conductingtemperature and then transmitting through them a normal or overloadalternating current.

2. The method of treating a glower for use in direct-current electriclamps which consists in heating it to conducting temperature, thenpassing an alternating current through it until it attains such acondition as to carry a normal direct current without material voltagevariation.

In testimony whereof I have hereunto sub scribed my name this 20th dayof March, 1901.

MARSHALL W. HANKS.

Witnesses:

H.-A. (Room, A. G. WEEKS.

